Width controlling means for cathode ray tube displays



Dec. 22, 1964 E. GOSTYN 3,162,791

WIDTH CONTROLLING MEANS FOR CATHODE RAY TUBE DISPLAYS Filed Feb. 5, 19632 Sheets-Sheet l INVENTOR. fen 52" 6057/ E. GOSTYN Dec. 22, 1964 WIDTHCONTROLLING MEANS FOR CATHODE RAY TUBE DISPLAYS 2 Sheets-Sheet 2 FiledFeb. 5, 1963 FIG. .9

INVENTOR.

[PA/55f aayrm/ Af/a/PA EXJ current in the horizontal deflectionwindings.

United States Patent 3,162,791 WHDTH @GNTRQLHNG MEANS FUR CATHQDE RAYTUBE DKSPLAYS Ernest Gostyn, Longrneadow, Mass, assignor to Generalinstrument (Corporation, Newark, Ni, a corporation of New Jersey FiledFeb. 5, W63, Ser. No. 256,459 16 Claims. (Cl, 317--2tl) The presentinvention relates to means adapted to be used in conjunction with acathode ray tube in order to control a single dimension of the display,and without deleterious effects on the desired shape (usuallyrectangular) 0f the display.

In a cathode ray tube display, such as that used for televisionreception, a beam of electrons is scanned laterally and vertically,thereby to sweep over that area of the screen where the display is to beproduced. Because of the diiferent characteristics of the horizontal(width) sweep, and the vertical (height) sweep, the means employed forcontrolling the extents of each sweep, and thus controlling the widthand height respectively of the picture display, should vary. Control ofthe extent of vertical sweep (height) is comparatively simple. However,control of the extent of horizontal sweep (width) generally presentsmore of a problem, particularly because of the rapidity with which thatsweep must be carried out, it being necessary that a large number ofhorizontal sweeps (usually in excess of two hundred) be carried out inthe period of time required for a single vertical sweep.

In most instances the electron beam is swept by means of magnetic fieldspassing through the neck of the tube and generated by windings mountedon the exterior of the tube. These windings generally comprise two setsof coils, one for controlling horizontal sweep and the other forcontrolling vertical sweep, these two sets of coils being designated ashorizontal and vertical deflection coils respectively. They aregenerally assembled on a specially designed support of insulatingmaterial so as to define a separately manufactured unit which can beincrease in the width, the horizontal sweep circuit would have to workharder because of the line voltage increase, and would also have to workharder because of the additional loading engendered by the action of thereactor in compensating for the increase in line voltage. It is to benoted that increased loading efifect derived from the reactor is due notonly to the fact that the reactor itself has losses, but also the factthat the introduction of the reactor into the circuit adversely changesthe transformation ratio of that circuit.

An alternative to the variable reactor is the use of a metallicconductive sleeve which is introduced into the magnetic field, usuallyin the cylindrical space between the glass neck of the picture tube andthe deflection yoke assembly. The eltect of this sleeve is electricallysimilar to that of the variable reactor-it affects the current in thehorizontal deflection circuit. It does so by acting as a shortedsecondary turn, eddy currents being induced therein, those eddy currentsin turn reacting upon the Hence use of such a metallic sleeve will, likethe variable reactor, increase the loading on the horizontal deflectioncircuit.

termed windows.

Patented ec. 22, 1964 In addition, the existence of the eddy currentsgenerates heat which may lead to failure of the deflection assembly.

Because of the complex requirements on both the horizontal and verticaldeflection fields, as well as the geometry of the display tube itself, atendency exists on the part of the display even in the absence ofattempts at width control, to depart from accurate rectangularity. Moreparticularly, the display tends to be larger at the corners thanelsewhere, giving rise to what has been very aptly termed pin cushioneffect. In order to minimize this effect compensating magnets are oftenemployed. Since these compensating magnets are usually fixed in positionand in strength in order to produce optimum eliect for a given magnitudeof the fields which produce horizontal and vertical deflection, anymodification of the deflection field so as to control the dimensions 'ofthe display is often accompanied by an increase in undesirable pincushion effect, even when only the horizontal deflection current ismodified.

It is the prime object of the present invention to provide a method forcontrolling, either in fixed or adjustable fashion, a single dimensionof the display (usually the width) in a simple and inexpensive manner,and in such a way as to avoid the disadvantages inherent in the priorart approaches to the subject as summarized above.

'More particularly, the arrangement of the present invention providesfor width control Without increasing the loading on the horizontaldeflection circuit to any appreciable extent. Moreover, the arrangementof the present invention lends itself readily to simple modification inorder to minimize, and in some cases largely eliminate, pin cushioneffect.

The structure of the present invention is specially designed to be usedwith a deflection winding which has axially extending conductor lengthsconnected by end turns, the Winding being formed in two diametricallyopposed coils each having two axially extending conductor lengthscircumferentially separated from one another by an appreciable space.Each of the axially extending conductor lengths of a given coil may belocated circumferentially adjacent to axially extending conductorlengths of the other coil. This type of coil arrangement list typifiedby the so-called saddle windings. The spaces between thecircumferentially inner peripheral edges of the adjacent conductorlengths of the two coils are here termed the butt sections of thewinding. The spaces between the circumterentially inner edges of thetwoseparated conductor lengths of each coil are here There are two buttsections and two windows for each pair of coils.

In accordance with the present invention control of the extent of thedeflection caused by a winding of the type described is achieved bylocating, substantially completely inside each butt section of thewiding, a segment formed of high permeability magnetic material. Thesesegments may be quite thin, and therefore may be conveniently interposedbetween the Winding in question and the neck of the tube on which thedeflection yoke together with its windings is mounted. These magneticsegments act as magnetic shields or shunts which by-pass some of themagnetic field generated by the horizontal windings, thus reducing theamount of the generated field which is rendered efiective upon theelectron beam for deflection purposes. When the segments are, asdescribed, located substantially completely circumferentially inside thebutt sections of the winding groups with which they are related, theywill have a maximum etfect upon the horizontal deflection field, andwill have no significant effect upon sociated with a given winding groupis formed of a plurality of circumferentially separated sections, widthcontrol is achieved and at the same time the tendency of the overalldisplay to assume pin cushion shape is minimized to a significantextent.

To the accomplishment of the above, and to such other objects as mayhereinafter appear, the present invention relates to a structure forcontrolling deflection in a single direction in a cathode ray tube orthe like, as defined in the appended claims, and as described in thisspecification, taken together with the accompanying drawings in which:

FIG. 1 is a side elevational View of a deflection yoke assemblyembodying the present invention and providing for adjustable control ofwidth;

FIG. 2 is a cross sectional view taken along the line 22 of FIG. 1;

FIG. 3 is a cross sectional view taken along the line 33 of FIG. 2;

FIG. 4 is a three-quarter perspective view of the adjustable elementshown in FIGS. 1-3;

FIG. 5 is a view similar to FIG. 4, but showing a specificiallydifferent adjustable element;

FIG. 6 is a front elevational view of a deflection yoke assembly inwhich the present invention is embodied in a fixed and non-adjustableform;

FIG. 7 is a detailed cross sectional view taken along the line 7-7 ofFIG. 6;

FIG. 8 is a side elevational view of a deflection yoke assembly similarto that of FIG. 6 but having a difierent type of vertical deflectionwinding thereon; and

FIG. 9 is a schematic cross sectional view of a typical deflection yokeassembly, such as that of FIG. 1.

In FIGS. 1-3 is disclosed a deflection yoke assembly comprising aninsulating support generally designated 2 which is adapted to be mountedon the neck of a television tube. The horizontal windings, generallydesignated 4, are mounted on the interior of the support 2, while thevertical windings d are mounted on the exterior thereof. A magneticallypermeable ring 8 surrounds the axially extending portions of thevertical windings 6, and is held in place by a clamp 10. The horizontalwindings 4 are of the saddle type, and comprise two coils or groups ofWinding 4A and 4B. The coil 4A comprises axially extending conductorlengths 12 connected by end turns 14 while the coil 43 comprises axiallyextending conductor lengths 16 connected by end turns 18. Thecircumfertially outer edges of the groups of conductor lengths 12 I and16 of the coils 4A and 4B respectively are located close to one anotherat 20 (see FIG. 2), but the circumferentially inner edges of each pairof conductor lengths 12 and each pair of conductor lengths 16 arerespectively circumferentially separated from one another by appreciablywide spaces 22. Those areas comprehended by the adjacent pairs ofconductor lengths 12 and 16 are here denominated the butt sections ofthe windings, while the spaces 22 between the butt sections of a givencoil 4A or 4B are called windows.

In the form shown in FIG. 1-3, the vertical winding 6 is also of thesaddle type, in that respect being similar to the horizontal windings 4,and is, as illustrated, mounted on the exterior of the insulatingsupport 2. The horizontal and deflection windings 4 and 6 are in spacequadrature with one another.

The deflection yoke assembly as thus far described is essentialconventional. The horizontal windings 4 and vertical windings 6 areseparately energized, and each produces a magnetic field at right anglesto the field produced by the other, and extending across the neck of thedisplay tube on which the assembly is mounted, those fields controllingthe horizontal and vertical deflection respectively of the electron beamwhich passes through the In accordance with the present invention, apair of segments 24 and 26 of high permeability ferro-magnetic material,preferably having low loss characteristics, are located inside thehorizontal windings 4A and 4B in such a position as to have partsextending in the same direction as the magnetic field produced by thosewindings. Reference may here be made to FIG. 9, in which the brokenlines 23 represent the magnetic lines of force of the field generated bythe horizontal windings 4A and 4B. t will be noted that the segments 24and 26 respectively extend across each adjacent pair of groupings ofwinding lengths I2 and 16, are substantially completelycircumferentially received within the confines of the butt sections ofthe windings 4A and 4B, and do not extend circumferentially into thewindows 22 defined between each adjacent assemblage of winding lengths12, 12 or 16, 16. Hence it will be apparent that the segments 24 and 26,since they are of high permeability magnetic material, act as shunts orby-passes for the magnetic field represented by the lines 28, thusreducing the amount of the generated field which is available for actualdeflection purposes. It will be appreciated that the degree ofby-passing of the horizontal deflection field can be controlled byvarying the size of the segments 24 and 26 which are elfectivelyinterposed in the field.

As disclosed in FIGS. 1-5, variation in the degree of magnetic fieldby-passing, and consequently the control of deflection width, isachieved by making the segments 24 and 26 adjustably axiallypositionable. T 0 this end the segments 24 and 26 are secured to, andproject axially out from, an insulating sleeve 36, the segments 24 and26 being occasionally flared outwardly and having a degree of inherentdeformability so as to tend to conform to the flared inner contours ofthe windings 4A and 4B. The tube 3t) is axially slidable inside thesupport 2 and the windings 4A and 4B and is adapted to be receiveddirectly over the neck of the cathode ray tube on which the assembly ismounted. As the tube 34 is slid in and out relative to the deflectionyoke assembly, the segments 24 and 2d slide with it, and hence more orless of those segments are operatively interposed into, and act asmagnetic shunts with respect to, the horizontal deflection fieldrepresented by the lines 23. In this way the etfect of that field on theelectron beam is modified, thus C011: trolling th width of the display.

It is to be emphasized that since the segments 24 and 2d aresubstantially completely received in circumferential registration withthe butt sections of the windings 4A and 4B, and do not extendcircumferentially into the windows-22 formed by those windings, andbecause the segments 24 and 26 are magnetically permeable and notprimarily electrically conductive, they will have no appreciable effecton the vertical deflection field generated by the vertical windings.

While FIG. 5 discloses an adjustable width member having segments 2 and26 each of a single piece (this corresponding also to the showing inFIG. 9), it has been found that effective width control is achieved, andat the same time specific control and minimization of pin cushiondistortion is achieved, when each segment 24 and Z6 is defined by asimilar plurality of separated sections 24A, 24B and 26A and 2613respectively. The segments 24A and 24B and the segments 26A and 26B aresimilarly designed and similarly symmetrically located. By thussubdividing the active area of the segments 24 and 26 the shieldingeffect produced by those segments is so modified as to tend to correctthe inherent pin cushion response of the deflection yoke, thus making itmuch easier to completely compensate for that effect through the use ofauxiliary magnets, such as those designated 32, and in some instancesmaking it possible to dispense with the use of such auxiliary magnets 32altogether.

While the vertical deflection winding 6 has, in FIGS. 1-7, beendisclosed as the saddle type, this is not essential, and FIG. 8discloses a deflection yoke in which the vertical windings 6' are of thetoroidal type, being wound about the magnetic core 8.

The embodiments of FIGS. 6-8 also diifer from that of FIGS. l-3 in thatthe magnetic segments 24 and 26, specifically shown with each segmentcomprising a pair of sec ions 24A, 24B and 26A, 26B respectively, arefixed in position rather than being adjustable. To this end the segmentsections are adhesively secured to an insulating strip 34 (see FIG. 7)which is in turn adhesively secured to the radially inner surfaces ofthe butt section of the appropriate horizontal Winding 4A or 4B. While,with this fixed and non-adjustable embodiment, compensation cannot bemade from time to time for difterent operating conditions, neverthelessthe fixed arrangement has been found to be very advantageous in reducingthe sensitivity of the horizontal deflection electromagnetic circuit bya predetermined selectable amount, in that way bringing about thedesirable result that the adjustment in width of the display image willnot significantly add to the loading effects on the sweep circuit bynormal variations in operating conditions, while at the same time, andparticularly where each segment is formed in a plurality of separatesections, as shown, the pin cushion effect is controlled and minimized.For low cost production of commercial television receivers, thisrepresents a substantial manufacturing advantage.

The particular shape of the segments 24 and 26 may be varied as dictatedby the geometry and electromagnetic characteristics of differentinstallations in order to produce optimum effects, both in the fixed andadjustable embodiments here disclosed. Moreover, in the adjustableembodiment the shape of the segments can be modified so as to bringabout a desired relationship between axial positioning of the segmentsand degree of width control achieved thereby. In those embodiments wherethe segments are divided into sections, it will be appreciated that thenumber of sections need not be limited to two, but instead three or moresections could be used for each segment. Fixed or adjustablecompensation can be effected, as desired, with yoke assemblies of eitherof the types of FIGS. 1 and 8.

It is exceedingly significant that with the arrangement of the presentinvention, in which magnetically permeable segments are utilized tomodify only a single dimension (here described in terms of the Width) ofthe display, and are therefore located substantially completelycircumferentially within the butt sections of the horizontal windings,the increased loading eifect of prior art approaches to the problem ofwidth control on the horizontal deflection circuitry is completelyeliminated. The increased loading of the prior art approaches isgenerally indicated by an increase in the cathode current of theamplifier tube in the horizontal sweep circuit, and is also reflected ina reduced boost voltage when the fiyback cycle deflection system isused, that boost voltage controlling the final anode voltage of thedisplay tube. It has been found that in connection with the presentinvention not only have these indications of increased loading not beenpresent, but, on the contrary, in many instances an actual reduction incathode current and an increase in boost voltage, and hence final anodepower, has been noted. This gives rise to a marked increase in picturequality.

The structure and arrangement of the present invention, and its assemblywith an otherwise conventional deflection yoke, is simple andinexpensive, and consequently excellently adapted to low price quantityproduction. Since it results in an actual improvement in the functioningof the deflection system, both in reducing loading, minimizing pincushion effect, and increasing picture quality, in addition toperforming its primary function of width control, it constitutes a verysignificant advance in the art.

While but a limited number of embodiments of the present invention havebeen here specifically disclosed, it

will be apparent that many variations may be made therein, all withinthe scope of the instant invention as defined in the following claims.

I claim:

1. In a cathode ray tube deflection assembly, a defiection windingcomprising substantially axially extending conductor lengths connectedby end turns, said axially extending lengths being formed into twocoils, the butt sections defined by said axially extending windinglengths being separated by windows, and a pair of substantiallydiametrically opposed segments formed of high permeability magneticmaterial, each circumferentially and radially located substantiallycompletely within a different one of said butt sections and extendingalong said butt sections substantially adjacent said windows.

2. The assembly of claim 1, in which the axial position of said segmentsrelative to their respective butt sections is adjustable.

3. In the assembly of claim 2, a sleeve of insulating material axiallyslidably received radially inside said deflection winding, said segmentsbeing mounted on said sleeve.

4. In the assembly of claim 2, a sleeve of insulating material axiallyslidably received radially inside said defiection winding, said segmentsbeing mounted on said sleeve and extending axially forwardly therefrom.

5. The assembly of claim 1, in which said segments are fixedly mountedrelative to their respective butt sections.

6. The assembly of claim 1, in which said segments are fixedly mountedon the radially inner surfaces of their respective butt sections.

7. In a cathode ray tube deflection assembly, a deflection windingcomprising substantially axially extending conductor lengths connectedby end turns, said axially extending lengths being formed into twocoils, the butt sections defined by said axially extending windinglengths being separated by windows, and a pair of substantiallydiametrically opposed segments formed of high permeability magneticmaterial, each circumferentially and radially located substantiallycompletely within a different one of said butt sections, each of saidsegments comprising a plurality of sections extending substantiallyadjacent said windows and separated from one another substantiallycentrally of said butt sections.

8. The assembly of claim 7, in which the axial position of said segmentsrelative to their respective butt sections is adjustable.

9. In the assembly of claim 8, a sleeve of insulating material axiallyslidably received radially inside said defiection winding, said segmentsbeing mounted on said sleeve.

10. In the assembly of claim 8, a sleeve of insulating material axiallyslidably received radially inside said deflection winding, said segmentsbeing mounted on said sleeve and extending axially forwardly therefrom.

11. The assembly of claim 7, in which said segments are fixedly mountedrelative to their respective butt sections.

12. The assembly of claim 7, in which said segments are fixedly mountedon the radially inner surfaces of their respective butt sections.

13. In a cathode ray tube deflection assembly, a deflection windingcomprising substantially axially extending conductor lengths connectedby end turns, said axially extending lengths being formed into twocoils, the butt sections defined by said axially extending windinglengths being separated by windows, and a pair of substantiallydiametrically opposed segments formed of high permeability magneticmaterial, each located in a circumferentially substantially centralposition relative to a different one of said butt sections and radiallyand circumterentially sub stantially completely within its correspondingbutt section, each of said segments comprising a plurality of sectionsextending substantially adjacent said Windows and separated from oneanother substantially centrally of said butt sections. I

14. The assembly of claim 13, in which the axial posi tion of saidsegments relative to their respective butt sections is adjustable.

15. In the assembly of claim 14, a sleeve of insulating,

material axially slidably received radially inside said de flectionwinding, said segments being mounted on said sleeve.

16. The assembly of claim 13, in which said segments are fixedly mountedon the radially inner surfaces of their respective butt sections.

References Cited by the Examiner UNITED STATES PATENTS 2,562,395 7/51Schlesinger 317-200 X FOREIGN PATENTS 777,722 6/57 Great Britain.

JOHN F. BURNS, Primary Examiner.

JOHN P. WILDMAN, Examiner.

1. IN A CATHODE RAY TUBE DEFLECTION ASSEMBLY, A DEFLECTION WINDINGCOMPRISING SUBSTANTIALLY AXIALLY EXTENDING CONDUCTOR LENGTHS CONNECTEDBY END TURNS, SAID AXIALLY EXTENDING LENGTHS BEING FORMED INTO TWOCOILS, THE BUTT SECTIONS DEFINED BY SAID AXIALLY EXTENDING WINDINGLENGTHS BEING SEPARATED BY WINDOWS, AND A PAIR OF SUBSTANTIALLYDIAMETRICALLY OPPOSED SEGMENTS FORMED OF HIGH PERMEABILITY MAGNETICMATERIAL, EACH CIRCUMFERENTIALLY AND RADIALLY LOCATED SUBSTANTIALLYCOMPLETELY WITHIN A DIFFERENT ONE OF SAID BUTT SECTIONS AND EXTENDINGALONG SAID BUTT SECTIONS SUBSTANTIALLY ADJACENT SAID WINDOWS.